The use of larger structures such as parts of a vehicle body or an aircraft fuselage in fiber composite design (e.g. carbon fiber reinforced plastic, CFRP, construction or fiberglass plastic, fiberglass, construction) may require protection of these structures against the effects of a lightning strike. The occurrence of the lightning strike is substantially analogous in the case of fiber composite components to the occurrence in metallic or electrically and thermally conductive structures. This results in the formation of a pre-discharge plasma channel and subsequently thereafter in lightning discharge. Depending on the location of the first point of contact, i.e. the point on the surface of the structure which is first contacted by the lightning, the lightning channel is then drawn across the surface of the structure to a first surge current discharge. With the contact of the lightning channel and the structure surface, a high flow of current and heat transfer is linked to the affected structure. The parameters which characterize the intensity of the lightning discharge do not differ, or do not differ substantially, between fiber composite structures and metal components. Typically, the thermal conductivity and the electric conductivity of fiber composite components are less, or significantly less, than that of metallic structures. A lightning protection can thus be necessary for fiber composite structures.
In the case of coated fiber composite structures, the direct lightning damage is substantially caused by an explosion of the lightning protection caused by the lightning strike. A lightning protection may consist of expanded copper foil which is laminated into an epoxy resin. The explosion of the lightning protection is caused by the direct heat of the plasma channel and by the Joule heat generated by the lightning current in the expanded copper foil.
For the protection of fiber composite structures against damage, in particular thermo-mechanical damage, during lightning strikes, expanded metal foils, in particular copper foils, are usually used. These expanded copper foils are applied as an outer stratum on an outer surface of the fiber composite structure and laminated into the fiber composite component. Expanded metal foils are advantageous due to the formability to a surface shape, for example on double-curved structures. For protection against environmental influences, this fiber composite structure is then protected with an electrically non-conductive dielectric paint. Due to the physical properties of such conventional dielectric coatings, a concentration or a constriction of a plasma channel arising during a lightning strike at the base point or point of impact can occur on the surface of the fiber composite structure during a lightning strike. Furthermore, such a coating can hinder or prevent a uniform spread of the base point of the lightning channel across the surface of the fiber composite structure. The direct heating of the plasma channel and the Joule heating of the lightning current can also lead to an explosion of the lightning protection layer, which is located beneath the coating.
Alternatively to a lightning protection having expanded metal foil, US 2008/0248275 A1 describes a lightning protection which consists of individual, overlapping graphene layers.